4.1. Symmetry/Asymmetry, Elliptical Fourier analysis (EFA)
and Modularity perspectives in skull development
Cranial asymmetry sheds light on developmental process disruptions in
species (Elliot, 2010) and pathological conditions involving the skull
(Elliot, 2006), it emphasizes relationship between structurally or
functionally interacting elements (Benitez et al., 2020). DA and
asymmetry studies are relatively scarce or non-existent in literature
for small African pangolins, FA is the bilateral asymmetry that
represents minute random developmental differences between a right and
its left side (Benitez et al., 2020). Klingenberg (2008) showed that
within the concept of geometric morphometrics studies of asymmetry can
be combined with other morphological issues – modularity and
integration. While modularity refers to the covariance among
morphological structures that originates in independent developmental
processes (so-called modules), integration; a counterpart to modularity,
is a measure of the interconnection among parts in order to function as
a whole unit (Klingenberg, 2008). Modules may be defined with respect to
genetic, developmental, functional or evolutionary context as being
currently interrogated. A low covariance (representing magnitude of
interaction among modules) is expected if two modulating units possess a
weak boundary suggestive of relative independence (Urbanova et al.,
2014); the converse is also true. Elliptical Fourier analysis is
fundamentally a mathematical application in the derivation of biological
closed shape outlines evaluations and valued for its automatization of
image analysis irrespective of morphological complexity for less
experienced users (Schmittbul et al., 2000). The method demonstrates
precise individual variations introducing scientific perspectives in
characterization of closed shapes such as the foramen magnum (Samuel et
al., 2017; Daegling and Jungers, 2000) in making useful inferences on
developmental instability in a population of samples.